The present invention relates to cellular communication systems, more particularly to user equipment in cellular communication system, and even more particularly to power saving operation of user equipment in a cellular communication system.
Cellular communication systems are well-known and are in wide-spread use around the world. FIG. 1 is a diagram illustrating a common feature found in most systems: a serving node 101 (depending on the system, it can be called a “base station”, a Node B, an evolved Node B (“eNodeB” or “eNB”)) serves user equipment (UE) 103 (e.g., a mobile terminal) that is located within the serving node's geographical area of service, called a “cell” 105. For convenience, the term “serving node” will be used henceforth throughout this document, but any such references are not intended to limit the scope of the invention to any one particular system. Thus, references to “serving node” are intended to also refer to “base stations”, “Node B's”, “eNodeB's”, “eNB's”, and also to any equivalent node in a cellular communication system.
Communication is bidirectional between the serving node 101 and the UE 103. Communications from the serving node 101 to the UE 103 are referred to as taking place in a “downlink” direction, whereas communications from the UE 103 to the serving node 101 are referred to as taking place in an “uplink” direction.
Traditionally, a UE uses a random access procedure to request a connection, and is paged when another entity wishes to establish communication with the UE. When there are no communications on-going, the UE conserves energy by entering an idle state and only waking up once every pre-defined discontinuous reception (DRX) cycle in order to check for a paging message.
With the ever spreading deployment of mobile broadband in combination with the ever-growing use of social networking, mobile communications have become more and more data oriented (as opposed to voice oriented). UE's are therefore frequently paged for data—rather than voice-related operations (e.g., receiving new comments from a friend, receiving push email) or they become active automatically in order to check for the presence of new messages on one or more web pages. In addition, popular smart phones also have other advanced applications, which consume a lot of electric and processing power.
The classical mobile network determined DRX mode of operation was designed primarily with voice communications in mind, and is not optimized to enable UEs to conserve energy in the context of these new data-oriented developments. Therefore, improved methods and apparatuses for dealing with idle mode are desirable.